Hi Kieran Can you explain the purpose of TCP_WND_UPDATE_THRESHOLD My MTU = 1500 WND = 512 MSS = 512
Med vänliga hälsningar/Best Regards Jan Wester WHI Konsult AB Scheelegatan 11, SE-112 28 Stockholm www.whi.se i...@whi.se +46 8 449 05 30 +46 705 36 77 22 -----Ursprungligt meddelande----- Från: lwip-users-bounces+j.wester=whi...@nongnu.org [mailto:lwip-users-bounces+j.wester=whi...@nongnu.org] För Kieran Mansley Skickat: den 14 oktober 2009 16:54 Till: Mailing list for lwIP users Ämne: Re: [lwip-users] TCP problem On Wed, 2009-10-14 at 16:21 +0200, Jan Wester wrote: > Hi > > I’m using lwip 1.3.0 and updated to 1.3.1 and found problem with > window size > > I receive small blocks of data (30 bytes) every 500 ms and on each I > call tcp_recved() > > On version 1.3.0 the window size on tcp ack is 512 (what is my > maximum), > > but for version 1.3.1 the window size Is decreased with the received > 30 until the size is less and it wait short time, > > after that the window size is 512 again and it continue. This is > repeated the hole time (I’m using the same application) Could you illustrate this with a packet capture? It sounds like you've got TCP_WND set to 512. It would be interested to know what your MTU and MSS is configured at, as having a window smaller than the MSS is not optimal. For example, this bug illustrates how a window that is always smaller than the MSS can cause problems: https://savannah.nongnu.org/bugs/?25882 NB. I don't think that is your problem, but may be of interest. The window advertisement code was re-worked in 1.3.1 to only send an explicit update when the change in window is greater than TCP_WND_UPDATE_THRESHOLD. This defaults to (TCP_WND / 4). You could define this to be zero to get the old behaviour, but the new behaviour should be much better. I would be interested to know what the problem you encounter as a result of the less-frequent window updates is. Note that any ACKs for data that get returned should have the up-to-date window information in them - it is only the sending of explicit window update ACKs that is restricted. Kieran _______________________________________________ lwip-users mailing list lwip-users@nongnu.org http://lists.nongnu.org/mailman/listinfo/lwip-users _______________________________________________ lwip-users mailing list lwip-users@nongnu.org http://lists.nongnu.org/mailman/listinfo/lwip-users
